This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPPthird generation partnership projectACKacknowledgeDCIdownlink control informationDLdownlink (eNB towards UE via RN)eNBEUTRAN Node B (evolved Node B)EPCevolved packet coreEUTRANevolved UTRAN (LTE)CDMcode division multiplexingCRCcyclic redundancy checkCQIchannel quality indicatorDeNBdonor eNBHARQhybrid adaptive repeat requestLTElong term evolutionMACmedium access controlMCSmodulation and coding schemeMM/MMEmobility management/mobility management entityNACKnot acknowledge/negative acknowledgeNDInew data indicatorNode Bbase stationOFDMAorthogonal frequency division multiple accessO&Moperations and maintenancePDCPpacket data convergence protocolPDCCHphysical downlink control channelPDSCHphysical downlink shared channelPDUprotocol data unitPHYphysicalPRBphysical resource blockRBradio bearerRLCradio link controlRNrelay nodeRRCradio resource controlRRMradio resource managementR-PDCCHrelay link (backhaul link) physical downlink control channelR-PDSCHrelay link physical downlink shared channelRVredundancy versionSGWserving gatewaySC-FDMAsingle carrier, frequency division multiple accessTBtransport blockTTItransmission time intervalUEuser equipmentULuplink (UE towards eNB via RN)UTRANuniversal terrestrial radio access network
The specification of a communication system known as evolved UTRAN (EUTRAN, also referred to as UTRAN-LTE or as EUTRA) is currently nearing completion within the 3GPP. As specified the DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.7.0 (2008-12), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (EUTRA) and Evolved Universal Terrestrial Access Network (EUTRAN); Overall description; Stage 2 (Release 8), incorporated by reference herein in its entirety. This system may be referred to for convenience as LTE Rel-8, or simply as Rel-8. In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the entire Release 8 LTE system.
FIG. 6 reproduces FIG. 4.1 of 3GPP TS 36.300, and shows the overall architecture of the EUTRAN system. The EUTRAN system includes eNBs, providing the EUTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE. The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME (Mobility Management Entity) by means of a S1 MME interface and to a Serving Gateway (SGW) by means of a S1 interface. The S1 interface supports a many to many relationship between MMEs/Serving Gateways and eNBs.
The eNB hosts the following functions:
functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling);
IP header compression and encryption of the user data stream; selection of a MME at UE attachment;
routing of User Plane data towards Serving Gateway;
scheduling and transmission of paging messages (originated from the MME);
scheduling and transmission of broadcast information (originated from the MME or O&M); and
measurement and measurement reporting configurations to provide mobility and scheduling.
Of particular interest herein are the further releases of 3GPP LTE targeted towards future IMT-A systems, referred to herein for convenience simply as LTE-Advanced (LTE-A).
Reference can be made to 3GPP TR 36.814, V1.2.1 (2009-06), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Further Advancements for E-UTRA Physical Layer Aspects (Release 9), incorporated by reference herein in its entirety.
A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. Current progress in 3GPP Ran-1 has shown that a Type-1 RN will be included in LTE Rel-10.
More specifically, section 9 of 3GPP TR 36.814, V1.2.1 states that relaying is considered for LTE-Advanced as a tool to improve, e.g., the coverage of high data rates, group mobility, temporary network deployment, the cell-edge throughput and/or to provide coverage in new areas.
The relay node is wirelessly connected to the radio access network via a donor cell. The connection can be inband, in which case the network-to-relay link share the same band with direct network-to-UE links within the donor cell. Rel-8 UEs should be able to connect to the donor cell in this case. The connection could also be outband, in which case the network-to-relay link does not operate in the same band as direct network-to-UE links within the donor cell.
With respect to the knowledge in the UE, relays can be classified as transparent, in which case the UE is not aware of whether or not it communicates with the network via the relay, or as non-transparent, in which case the UE is aware of whether or not it is communicating with the network via the relay.
Depending on the relaying strategy, a relay may be part of the donor cell, or control cells of its own. In the case the relay is part of the donor cell, the relay does not have a cell identity of its own (but may still have a relay ID). At least part of the RRM is controlled by the eNB to which the donor cell belongs, while parts of the RRM may be located in the relay. In this case, a relay should preferably also support LTE Rel-8 UEs. Smart repeaters, decode-and-forward relays and different types of L2 relays are examples of this type of relaying.
In the case where the relay is in control of cells of its own, the relay controls one or several cells and a unique physical layer cell identity is provided in each of the cells controlled by the relay. The same RRM mechanisms are available, and from a UE perspective there is no difference in accessing cells controlled by a relay and cells controlled by a “normal” eNB. The cells controlled by the relay should support also LTE Rel-8 UEs. Self-backhauling (L3 relay) and “type 1 relay nodes” use this type of relaying.
3GPP TR 36.814, V1.2.1 also states that at least “Type 1” relay nodes are part of LTE-Advanced. A “type 1” relay node is an inband relaying node characterized by the following: it control cells, each of which appears to a UE as a separate cell distinct from the donor cell; the cells shall have their own Physical Cell ID (defined in LTE Rel-8) and the relay node shall transmit its own synchronization channels and reference symbols, etc. In addition, in the context of single cell operation the UE shall receive scheduling information and HARQ feedback directly from the relay node and send its control channels (SR/CQI/ACK) to the relay node. In addition, the relay node shall appear as a Rel-8 eNB to Rel-8 UEs (i.e., it is fully backwards compatible with Rel-8 UEs. Further, to LTE-Advanced UEs it should be possible for a type 1 relay node to appear differently than Rel-8 eNodeB to allow for further performance enhancements.
As was noted above, it is already assumed in 3GPP TR 36.814, V1.2.1 that a wireless DL backhaul (i.e., the link from the DeNB to the RN) will be implemented in a Rel-8 backwards compatible fashion. This is accomplished by configuring a MBSFN subframe in the RN cell. One difference between the backhaul link and a normal link, i.e., that between the DeNB and a macro cell UE, is that for the former the data traffic for multiple UEs under the RN cell is aggregated. By reusing LTE Rel-8 mechanism, data traffic of different QoS types will be bundled over the backhaul link to form a transport block (i.e., a TB). As a result, the physical layer can handle the TB by using Rel-8 procedures, which implies one R-PDCCH channel for granting the resources, and one ACK/NACK feedback in the UL. This approach, however, suffers from a lack of efficiency as identified in R2-094637, 24-29 Aug. 2009, 3GPP TSG-RAN WG2 #67, “Number of MAC PDUs for Relay Operation”, LG Electronics Inc., since the traffic of different QoS type will have to be treated equally in terms of scheduling and HARQ operations.
It has been proposed that the backhaul can possibly support multiple TBs in a single subframe (R1-093388, 24-28 Aug. 2009, 3GPP TSG-RAN WG1 Meeting #58, “Considerations on Multiple HARQs in Type I Backhaul Link Transmission”, Samsung. One possible benefit is that the traffic of different QoS types can be embedded into different TBs and thus treated accordingly.